Race Engine Forum UK

Hello Guy
I have an 82' Fiat spider with fuel injection the engine was recently modified as follows:
-Allison snake header
-ca. 9.8-1 static CR pistons 84.5mm
-oversized valves
-developed combustion chambers
-ported and/or polished intake/exhaust
-lightened flywheel
-system balanced
-Miller's Mule cam timing wheels
-Allison's mild street cams

My question is this: there is talk of a new supercharger kit coming on the market that would utilize the sprintex supercharger, with the above mentioned engine mods do you think this would give me some more kick? I'm a bit concerned about my static CR of 9.8 although that may mean little considering my mods and what the true dynamic CR would be. I believe the system will also come with its own self-teaching ECU. Thanks
Mike Freeman

in short -

"..with the above mentioned engine mods do you think this would give me some more kick.."

very briefly until the engine blows up...

GC

Guy
Could you please elaborate. Thanks.
Mike

Many will disagree I am certain of that - but in my expert opinion - a supercharged engine should be built from scratch.

Starting with low compression forged pistons - even the old Lancia and Fiat pistons for supercharged engines had thicker crown and ring lands.

Sodium-cooled ex valves and bronze guides are a must-have, plus a head gasket way stronger than your will currently be.

G

Strongly approve Guy on this one!

I have blown many stock NA motors having as little as 8.9:1 CR with just 8psi of boost! (Only to rebuild them properly of course). We used to test turbo setups on old BMW M30 engines. Install the whole setup, make the modifications, test drive it until the engine blows, then when everything is right about the setup, build a correctly stuffed engine. But hey! Those motors cost only 300$ in our scrapyards!

So when building properly, get forged low-compression pistons (From Guy), forged rods (again from Guy), reinforced head gasket (Guy, again), and head studs kit. Oh, and take his advice too on camshaft setup, this will be very useful. I'm only advising Guy because his material is proofed fail-safe, over and over again.

As for ECU tuning on a turbo/super charger, stay on the very safe side too. Start from a rich mixture and lean it up by little increments as you go. Not the other way around.

Believe me, in way faster than a blink of the eye, a supercharged setup incorrectly done, can leave you with a hole in the crankcase, and some aluminum powder in the bottom of the sump.

Good luck and happy holidays!

N

Thank you all, for your input. I figured it was a long shot, just wish I had thought of it before I did the engine rebuild, although it would have added considerable cost to the job. Happy New Year.
Mike

yes, the sad reality (and it is a reality) Mike is that attempts to increase power of normally-aspirated engines by attaching any means of pressure-charging are doomed to failure!

G

This reminds me of an American program I was watching the other week.

The guys purchased an old Jaguar XJ12 and without any modification fitted a huge supercharger and holley carbs on top of the block.

Not surprisingly it ran for about 30 minutes before it disintegrated! I guess 30 minutes was quite an achievement.

Was quite amusing to watch though with its huge holley intakes sticking up through a cut out in the bonnet!